I haven’t actually built these two classes out, as I’m not intending to allow PCs to take them. But as a rough sketch …
Aristocrats are combat-hardened nobility, equally at home on the battlefield and at a fancy dinner. They are functionally fighters whose prime requisites are STR and CHA, who start with Diplomacy and the bard’s Inspire Courage ability, and gain Leadership later (and can take Leadership separately as well). At ninth level, aristocrats can construct a stronghold, just like fighters.
Diplomats are the rest of the nobility. They are built as thieves whose prime requisite is CHA, but the only thief skills they possess are Move Silently, Hide in Shadows, and Backstab; they start with Diplomacy, Intimidation, and Seduction, and gain Loremastery, Dabble in the Arcane, and Leadership later (and can take Leadership separately as well). At ninth level, diplomats can construct a stronghold, just like fighters.
Both classes generally have significant cash. Aristocrats receive a monthly stipend of 1d3×60 gold per month (equivalent to a 10% stipend from a March owned by the family) and diplomats 1d3×30 gold per month (5%). Both start with 10× this amount at 1st level for starting gear. This stipend does not contribute to XP.